Correct field names for Adafruit IO to match website

Author: tyeth

CircuitPython_Templates/adafruit_io_cpu_temp_neopixel_color/code.py

@@ -48,8 +48,8 @@ def message(client, feed_id, payload):  # pylint: disable=unused-argument
 # Initialize a new MQTT Client object
 mqtt_client = MQTT.MQTT(
     broker="io.adafruit.com",
-    username=os.getenv("ADAFRUIT_IO_USERNAME"),
-    password=os.getenv("ADAFRUIT_IO_KEY"),
+    username=os.getenv("ADAFRUIT_AIO_USERNAME"),
+    password=os.getenv("ADAFRUIT_AIO_KEY"),
     socket_pool=pool,
     ssl_context=ssl.create_default_context(),
 )